Hey all. So just done my tax return and am already thinking of ways to blow it. I am contemplating wider rubber and new rims for the Yeti Sled.

Just wondering how wide is too wide. Not so much as a fitment problem, as i have extremely adjustable suspension, and no problen taking a sawzall to my fenders, then bolting on over fenders, flares etc. Im more wondering as a performace trade off?

Is there a point where it gets so wide, that you no longer see improvements in grip?
Hypotheticaly, would you notice extra grip going from say 235 to 295, and would that improvent be linear. Ie the tyres are 25% wider. Would that equate to 25% more grip?
Is extra width with compromised wheel alignments (camber) better than less width with ideal alignment?

Is there a way to work out how much heavier tyres get as they go wider?

I currrently have Gmax Drift 6 in 17x8, with Hankook Z221 235/45 soft. Im thinking of stepping up to maybe a 18x10ish and 265 or wider. Obviously 265 aint gonna fit a Forester with out a lot of jiggery-pokery. So if your gonna go crazy with cutting fenders out and bolt on flares etc, then you may aswelll go as wide as you can. Problem there is that there isnt a whole lot of size options past 265 for Rcomps like Hankooks or Yokos. They basically go 265 straight up to 295. The hankooks do have a 285 though.

And 295 is bloody wide. Like really really really wide. And I dont even know if its possible to go that wide on a forester? Its definitely not practical. It might be so wide my engine will struggle turning the big heavy things. Ive never been much of a fan of hella-stance or whatever. If i was to do such a ridiculous thing, it would be purely for grip performance gains at the track. So it would have to work, and still retain things like suspension bump travel and not rub off all the tread from those expensive tyres.

Im thinking Rays Volk Ze40 Face 3 Gunmetal Blue 18x10+35 5x114.3. With 295/30R18 rubber. (Am i dreaming?) 10inch wide because you can fit anything from 265/35 up to 295/30 on that width rim. (so it leaves options open if i pull the pin on a set of new rims). 35 offset maybe a bit too much inwards? It will be a few mms from my struts and trailing arms etc. But next size out is 20, and that will be too much poke, even with fender flares. So 35 offset with the possibility of 5mm-ish hubcentric spacers if need be. Brake clearance shouldnt be an issue i hope? I have Wilwood 330mm 6pots, which are a forged narrow caliper. (I do like the idea of 18s as that leaves the door open to upgrade the Wilwoods to the 350mm rotor varients) Wheel arch liners will need to go. Fenders will need to be chopped and flares bolted on over. Ride height will probs need to go up a smidge aswell. I will put my 25mm front swaybay on to help control corner roll (and rubbing), and probably have to upgrade the rear from 22 to 24 or there abouts for the same reason.

Just brainstorming at the moment. Thoughts. Is this a retarded idea?

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Doing it for all the wagons out there

If its a track purpose ask your self these questions .

What are my grip and traction limitations at the moment .
What handing balance and characteristics does the car have at the moment .

Is the bigger footprint going to have a positive or negative affect on your driving style . Its really a personal question from your point of driving as in what do you want from the experience .

For instance the size rubber I run I like because the car moves around alot but is very controllable and it puts a smile on my face, because the fun factor is there for me . But #1 for me is enjoyment not being ultra competitive. If I went wider my times would improve but It would lose the fun factor for me so I say no. Even though wide rubber looks frikkin awesome .

That is a great point. I already feel I could do with more grip. But thats probs my driving technique (or lack there of) and probably the car not set up at its optimum.

As it is now, the car tends to oversteer a bit on most of the corners at RAC, and only understeer on really tight turns etc. Its really really fun to throw it around now. Im only just getting used to it aswell, and there is probably loads of room to improve with driver and car setup first as it is.

But, im always thinking of ways to make the car more bad ass. And angry wide rubber would do that.

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Doing it for all the wagons out there

I doubt 'grip' is linear to width, what you're probably hunting is more lat/long acceleration. This would require a balanced suspension set up - ie each component and spec complements eachother, not just dial in any old 'feels good' settings independently.

Tyre weight - maybe manufacturers spec sheet or a nasty approximation density x volume. Also increased rolling resistance and inertia from more weight and contact.

As said above, what are your current limits? IMO smallest footprint with good cornering ability is ideal, so "better rubber and less of it" kinda thing.


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Slow is smooth and smooth is fast.

Good points. I know the car is far from setup. I have just basically thrown a bunch shiny parts at it then put it on the track, with no real trial and error adjusting stuff. Im not a race engineer, and cant really say what works in harmony. Or even begin to disect what i currently have, to see what needs to be altered to improve stuff. But a simple-tons view is that if im sliding around now, then more grip would help, ergo wider tyres.

The wheel weight is lower. Those 18x10 Ze40s weigh less than my current 17x8 Drift 6s. (Just by 1-200 grams.) But they are 2inch wider, and 1inch bigger, and 10000000x more sexy. Tyres on the other hand would definitely add more weight. A basic guess that im pulling out of my arse is 25% wider would be maybe 20% heavier.

Currently have hankook Z221 in soft compound in 235/45/17. I think the only better semi slick rubber in that size would be the yoko A050. Or go to a full slick maybe.

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Doing it for all the wagons out there

Have you considered set of AO50's in your current size first? The people I know who have gone from the Hankooks to them say they would not go back to Hankook, not because they are shit but because the yoki's are that much better in terms of lateral grip.

If 10 inch wide rims can be fitted to a GC (Roughstilin) then I reckon it can be done to a Foz. If you saw the pics in my build thread my tyres are rubbing the arch liners that are 10mm away from the tyre surface. Your car probably wouldn't flex as much because you have deleted all the rubber mountings but you still don't want your tyre/rim less than 5mm from the strut from what I have been told.

Have you had a chat with John Fowler? I went through this with him about my Betty and he recommended staying with my oem size rims as weight starts becoming a factor at my modest power level and the sprint racing I am interested in is a bit more about chucking the car around and having fun.

A dedicated Barbs car you might see gains but not sure for sprint series/rally style events.

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Bye bye betty blue. Hello F6.

Yeah, I did have a chat with John briefly at the previous RAC sprint about maybe commissioning him to sort my rig out. But I havent done so yet. I really need to book some time off work and book some time in with him. I only just had this crazy idea last night. I did get John at the barbs training night a few months back as my instructor, and he certainly inspires confidence.

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Doing it for all the wagons out there

I also get what you guys are saying about keeping it fun. Last thing i want to do is detract from that. Super big tyres might stick like shit to the road, but then i might lose the ability to do a skid. And lose a bit of straight line speed. I dont want that.

And buying tyres in that size every year wouldnt be so fun either.

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Doing it for all the wagons out there

Yeah I was gonna mention the cost factor next.

My hankooks will be coming off in a couple of weeks (245*40*18) moving to AO50's.

If you want to test a bigger wheel size before then (18*8.5 +55 offset, PCD 114.3, lightweight BBS oem rims) with hankooks you are welcome to come and test them on your Foz.

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Bye bye betty blue. Hello F6.

JOHN FOWLER spend your money on a wheel alignment with him . Tell him what the car does and ask him to try and eliminate the bad traits .

Then after much fun when you have reached the limits of that set up look at wider Rcomps etc . Reaching the limits of your mass amounts of lightweight shiny shit should take you a lifetime anyway lol = lots of epic fun times .

Probably the best person for tyre advice as well .